1. FIELD OF THE INVENTION
The present invention relates to a container, and more specifically, to a freight container with an increased door opening height in which the thickness of the door header is reduced without changing the external dimensions of the freight container's rear end frame. Moreover, the floor slopes downward towards the doorway in order to increase the height of the door opening, thereby increasing the effective capacity of the freight container and the efficiency with which it can be loaded.
2. DESCRIPTION OF THE RELATED ART
Freight containers are used to hold freight while it is being transported by land, sea or air. Their widespread use on ships, planes, trucks, and trains requires that they be made to withstand the rigor of travel, while also conforming to international standards of dimension so that they are compatible with such a spectrum of transport vehicles, for example, the various dimensions identified by the International Standard ISO 668, fifth edition, Dec. 15, 1995, the contents of which are hereby incorporated by a reference. One such example of a prior art freight container conforming to the International Standard ISO 668 is a Series 1A freight container which has a minimum door opening dimensions of 2.134 m.times.2.286 m, external dimensions of 12.192 m.times.2.438 m.times.2.438 m, an internal volume of 1 m.sup.3 and minimum internal dimensions of (the nominal container external height--241mm).times.2.330m.times.11.998m. The door opening dimensions of the freight containers are particularly important factors affecting the efficiency with which freight can be loaded and unloaded.
The prior art will be now explained in detail with reference to FIG. 1, which is a perspective view of a conventional freight container, and FIG. 2, which is a perspective view illustrating the freight container in FIG. 1 from another angle. The framing of a conventional freight container 1 is hexahedral in shape. The front end frame 20 and rear end frame 30 are disposed on a base structure 10 and are connected to each other by an upper frame 40 and a lower frame 50. A plurality of panels are arranged on the top and sides of this hexahedral skeleton to form a roof 3 and side walls 5, respectively.
FIG. 3 is an exploded perspective view illustrating the structure of the rear end frame of a conventional freight container, and FIG. 4 is a front view illustrating the rear side of a conventional freight container, and FIG. 5 is a schematic side c ross-sectional view illustrating the base structure of a conventional freight container.
The rear end frame 30 of the conventional freight container 1 includes a door sill 32, which serves as a threshold at the rear side of the base structure 10, and a corner post 34 disposed on each end of the door sill 32. On the tops of the corner post 34 is mounted a door header 36. Corner fittings 38 are provided at each point where the corner posts 34 are jointed to the door header 36 and the door sill 32. The hinges 65 connect each door 60 to its respective corner post 34 so that a given end door 60 is rotated on its hinges 65 to a fixed angle when the door 60 is opened.
As shown in FIG. 5, the base structure 10 includes a plurality of floor bearers 12 spanning the width of the freight container and a floor 14, which is also connected to the door sill 32, mounted thereon in such a way that it is level with the door sill 32. In the freight container 1 configured as above the door opening height, measured as the distance between the top surface of the door sill 32 and the bottom surface of the door header 36, is affected by the thickness of the door sill 32 and door header 36. If the thickness of the respective door sill 32 or door header 36 is increased, the door opening height is decreased to that extent.
On the other hand, the thickness of the roof 3 is thinner than that of the door header 36, and therefore the internal height of the freight container, measured as the distance between the top surface of the floor 14 and the under surface of the roof 3, is greater than the door opening height. Therefore, even though a palletized cargo of the appropriate height is sized to fit inside the freight container, it would not be able to be loaded through the doorway due to the relatively low door opening height. Accordingly, the size of palletized cargoes to be loaded into the freight container is restricted by the door opening height, wasting space at the top of the freight container.